Humans have been applying tattoos to the skin for over 8000 years. The inks and dyes used were historically derived from substances found in nature and comprise a heterogeneous suspension of pigmented particles and other impurities. A well-known example is India ink, a suspension of carbon particles in a liquid.
Tattoos are typically produced by applying, with tattoo needles, tattoo ink into the dermis, where the ink remains permanently. This technique introduces the pigment suspension through the skin by an alternating pressure-suction action caused by the elasticity of the skin in combination with the up-and-down movement of the tattoo needles. Water and/or other carriers for the pigment introduced into the skin diffuse through the tissues and are absorbed. The insoluble pigment particles remain in the dermis where they were initially placed, for the most part. Inks used for tattooing resist elimination by virtue of their inertness and the relatively large size of the insoluble pigment particles. A tattoo produced in this manner will partially fade over time but will generally remain present throughout the life of the tattooed person.
Tattoos are used for a variety of reasons, primarily for ornamentation of the skin. While tattoos have traditionally been applied as designs for the skin, they are also used for permanent cosmetics, such as eyeliner and lip color often by people who cannot apply makeup, such as those suffering from arthritis or Parkinson's disease. Additionally, for breast reconstruction after mastectomy, it is desirable to reconstruct the nipple and areola area with darker flesh tone tattooing in order to produce a natural-looking breast. Moreover, tattooing has been used to treat hypo- and hyper-pigmentation caused by vitiligo, skin grafts, port-wine stains, and other dermatologic conditions.
Quite often people have a change of heart after being tattooed. For example, a person may desire to remove or change the design of a decorative tattoo, such as the name of an old girl friend after the tattooed persons marries someone else. Alternatively, an individual with cosmetic tattooing, such as eyeliners, eyebrows, or lip coloring, may wish to change the color or area tattooed as fashion changes. In addition, following breast reconstruction, the geometry of the breast may change over time, leading to a tattooed nipple changing from an aesthetically pleasing position to an unpleasant one.
Unfortunately, there is currently no simple and completely successful way to remove tattoos. Removal by surgical excision, dermabrasion, requires invasive procedures associated with potential complications, such as infections, and usually results in conspicuous scarring. Removal by laser therapy is the most common technique and is usually limited to eliminating only from 50–70% of the tattoo pigment, resulting in a residual smudge. Laser removal requires multiple treatment sessions (usually five to twenty) with expensive equipment for maximal elimination. Thus, the overall cost of laser removal is generally prohibitively expensive for many people. Additionally, most tattooing inks are made of pigments which have a wide range of particle size. If the pigment particles are small, they may diffuse through the tissues, causing “bleeding” of the color, “blurring” of the lines of the tattoo, or partial fading of the tattoo.
Prior art temporary substitutes for tattoos are unsatisfactory because they tend to be very short-lived. If only the surface of the skin is colored, such as by painting on the skin, the ornamentation is easily removed by wetting or rubbing the skin or by the natural sloughing of epidermis every three to four weeks. While this technique produces only temporary skin ornamentation, it would be desirable to have the option to color the skin to last longer than a few hours, days, or weeks.
The epidermis, 39 in FIG. 1 and FIG. 1A of the human skin comprises several distinct layers of skin tissue. The deepest layer is the stratum basale layer which consists of columnar cells. The next layer up is the stratum spinosum composed of polyhedral cells. Cells pushed up from the stratum spinosum are flattened and synthesize keratohyalin granules to form the stratum granulosum layer. As these cells move outward they lose their nuclei and the keratohyalin granules fuse and mingle with tonofibrils. This forms a clear layer called the stratum lucidum. The cells of the stratum lucidum are closely packed. As the cells move up from the stratum lucidum they become compressed into many layers of opaque squamas. These flattened cells have become completely filled with keratin and have lost all other internal structure, including nuclei. These squamas constitute the outer layer of the epidermis, the stratum corneum. At the bottom of the stratum corneum the cells are closely compacted and adhere to one another strongly, but higher in the stratum they become loosely packed and eventually flake away at the surface. Also shown in FIG. 1 is hair stem 33 sebaceous gland 38, hair duct 31, nerve ending 34, veins and arteries 36 and 37, sweat gland 35 and pupilla 32.
It is known that graphite vaporizes at about 3,600.degrees. C. It is known that graphite is a strong absorber of infrared light and that infrared light such as the 1.06 micron laser beam produced by the Nd:YAG laser will penetrate several millimeters through human skin. It is also known that short pulses of light energy absorbed by a strongly absorbing material can result in shock waves creating mechanical forces.
What is needed is a better method for applying tattoo quickly and without needles and pain.